Example embodiments of inventive concepts relate to a semiconductor memory device, and more particularly, to a nonvolatile memory device including a coupling program control unit and/or a method of operating the same.
Semiconductor memory devices may include volatile memories, such as DRAM and/or SRAM. Semiconductor memory devices may also include nonvolatile memories such as EEPROM, FRAM, PRAM, MRAM, flash memory, and the like. A volatile memory may lose data stored therein at power-off, while a nonvolatile memory may retain data stored therein even at power-off. In particular, a flash memory device may have merits such as a high programming speed, low power consumption, a mass storage capacity, and the like. For this reason, the flash memory device may be widely used as a storage medium of a computer system.
A flash memory device may store single bit data or two or more data bits (or, referred to as a multi-bit data) per memory cell. A flash memory device storing single bit data per memory cell may be referred to as an SLC flash memory device, and may have an erase state and a program state according to a threshold voltage distribution. A flash memory device storing multi-bit data per memory cell may be referred to as an MLC flash memory device, and may have an erase state and a plurality of program states according to a threshold voltage distribution.
In the MLC flash memory device, it is important to secure the read margin between program states. However, threshold voltages may vary due to various factors at programming.